It is not necessary to drink laxatives two days in advance of a colonoscopy. Usually 4-6 hours before the colonoscopy oral intestinal cleansing drugs, in 2 hours to drink. If the standard of bowel examination is not met, then additional medication is needed, but the total amount should not exceed 4L. Before doing colonoscopy, you need to drink laxatives to clean the intestinal tract for better observation of the intestinal tract, and the commonly used medication is Compound Polyethylene Glycol Electrolyte Dispersant (CPGED), the specific method of taking is to dissolve two bags of CPGED in 2L of warm water and mix well, and then take 250 ml of CPGED every 15 minutes. in case of severe abdominal distension or other discomforts, continue to take the medication after the symptoms are eliminated, and continue to take the medication until you pass the watery stools. Colonoscopy is an invasive test, it is recommended that patients eat fluids or semi-liquids, such as millet porridge, noodles, etc., the day before the examination, which is conducive to the complete emptying of the intestinal tract. The specific method of administration is recommended to strictly follow the doctor’s instructions.